Why we made Mattermost an open source Slack-alternative

Mattermost web experience, with pre-set as well as full customizable color themes.

The company that builds Mattermost was founded in 2011 as “SpinPunch, Inc”, an HTML5 game engine developer. To demonstrate our technology, we built a massively multiplayer, real-time strategy game title called “Mars Frontier” and published it on Facebook. A month later, we received investment from Y Combinator, a seed-stage investment fund in Silicon Valley. Over the summer–as Mars Frontier grew, and the game engine market fizzled–SpinPunch shifted from engine developer to games studio.

Mattermost “Version 1” began in 2013, as a project to reach gamers outside of Facebook, by turning SpinPunch.com into a HTML5 games portal and messaging app.

Ironically, while we were building communications software for our users, our company’s internal communications were failing. In 2013 (before Slack), we relied on another popular team messaging service, which became plagued with issues after it was sold to a large company. The service slowed. It froze. It crashed. It lost data. We tried to leave, but its export function broke. We asked other YC companies for advice. Half the companies responding used the same deteriorating service. Many felt just as trapped as us, because there weren’t good alternatives. We’d been using messaging instead of email for over a year, and it was impossible to go back. We needed a new solution.

The seed of Mattermost occurred then, but before it could take root a new priority arose: Our second game title, “Thunder Run: War of Clans”, started suddenly growing. It amassed a niche following and won Facebook’s “Best New Games: Hardcore Strategy” award in 2013. We stopped work on everything else to build more game content.

In 2014, Slack became popular in Silicon Valley, and our company adopted it for messaging. But we had a problem–our archives were in our old messaging app. After our subscription expired, the old app wanted us to pay them to access our own data (and export still didn’t work!). We hated being locked in. We fumed. Our discussions, our research, our analyses, and gigabytes of our carefully tagged in-game artwork was all held for ransom by the service we had trusted. Slack was good, but it was another proprietary SaaS app, and we’d just been burned.

So we decided to build our own.

Since SpinPunch.com was to be a messaging app and a games portal, we could build the messaging features first–use that for company communication–and add the game portal later. With that plan in mind, we built “Version 2”. Our team moved internal messaging to this version as soon as we could, leaving Slack behind.

Along the way we decided to open-source our work. We began 2015 with a re-write in Golang and React. This “Version 3” had a simplified architecture and a web UI working across PCs and phones.

Mattermost mobile experience adding comments and sharing files.

We renamed the project “Mattermost” to emphasize the importance of communication. We believe that 1) internal messaging–across PCs and phones, with file sharing, archiving and search–is a vital layer of IT in a “post-email” world, 2) the platform for internal messaging needs to be open, and 3) that we wanted Mattermost to be the leading project to serve as the open layer for internal communications.

To get early feedback, we made our code public on June 24, 2015 as an “Open source, on-prem Slack-alternative”. The announcement trended to the top of Hacker News, where we got repeated requests for “why did you build this?”